This invention describes a method for producing silicone elastomers from dual functional siloxanes. Methods for forming elastomers from two-component or two-part room temperature vulcanizing (RTV) silicones are well-established in the art. A typical two-component system based on an “addition” or hydrosilylation cure consists of a Part A, which contains a vinyl-functional base polymer, a catalyst, and optionally a reinforcing component (such as a siliceous component or reinforcing resin and pigment), and a Part B, which typically contains the same vinyl-functional base polymer and a hydride-functional crosslinking polymer. When the two parts are mixed, the crosslinking reaction commences and an elastomer forms. The rate and temperature of cure depend on the nature of the catalyst and various modifiers and inhibitors of the catalyst function. This simple system works well for traditional silicone elastomers, but is not effective for step-growth elastomers which do not rely on crosslinking, but rather on the formation of extremely high molecular weight linear polymers. Any low-molecular weight functional contaminant is likely to destroy the near perfect stoichiometry of these materials, precluding optimum property development and introducing volatile or extractable species. One possible way of creating a two-component system is to disperse the hydrosilylation catalyst in a high molecular nonfunctional silicone. However, practically speaking, if the molecular weight of the silicone is high enough to avoid interference with optimum property development, it is also too highly viscous to allow facile mixing.
A method for producing silicone elastomers from dual functional siloxanes is described in U.S. Patent Application Publication No. 2013/0041098 of Arkles et al. However, in some cases, it may be difficult to form elastomers with consistent properties using the methods described therein due to the difficulty in providing consistent mixing of the dual functional siloxanes with the curing catalyst. One obvious method of addressing this problem is to perform a continuous process in which the catalyst and polymer are fed at controlled rates into a mixing device, such as a static mixer or extruder, yielding consistent elastomers. However, in relatively small applications, design requirements of continuous or computer-controlled mixing may not be practical. Accordingly, a method for producing silicone elastomers from dual functional siloxanes that would be applicable to both small and large scale reactions would be desirable.